Double embryo transfer with mosaic embryos: experience from a large academic fertility centre

What are the overall, singleton and twin live birth rates (LBR) after a double embryo transfer (DET) involving mosaic embryos?

This was a retrospective cohort study of DET with at least one mosaic embryo between 1 December 2016 and 1 December 2024. Each DET was assigned a prognostic score (A-F) based on the ploidy of both embryos. The primary outcome was the overall, singleton and twin LBR of good-prognosis (A and B), moderate-prognosis (C and D) and poor-prognosis (E and F) DET. Secondary outcomes were the LBR for mosaic/mosaic compared with euploid/mosaic transfers. Comparisons were also made with previously published data on euploid/euploid transfers.

In total, there were 38 DET: 22 mosaic/mosaic and 16 euploid/mosaic. Twenty-nine (76.3%) patients had prior failed euploid transfers, and 19 (86.4%) mosaic/mosaic patients did not have any euploid embryos. The differences in overall LBR between the prognostic groups did not reach significance [65.0% (13/20) good-prognosis group versus 71.4% (5/7) moderate-prognosis group versus 45.5% (5/11) poor-prognosis group; P = 0.5]. The twin LBR was higher in the good-prognosis group (46.2%) compared with the moderate- and poor-prognosis groups (0% for both; P = 0.04). Overall [72.7% (16/22) versus 43.8% (7/16); P = 0.07], singleton [54.5% (12/22) versus 31.3% (5/11); P = 0.20] and twin [18.2% (4/22) versus 12.5% (2/16); P = 0.6] LBR were similar between mosaic/mosaic and euploid/mosaic DET. While the multiple LBR was high in both groups, it was lower for mosaic/mosaic and euploid/mosaic DET compared with euploid/euploid DET [26.1% (6/23) versus 49.8% (113/227, previously published data); P = 0.04].

Caution must be exercised with mosaic embryos as they can behave like euploid embryos, and DET can result in twins. DET with moderate- or poor-prognosis mosaic embryos had lower twin rates and may be reasonably considered. Larger studies are needed.